It is probably safe to say that the natural building materials such as soil, wood and stone have been used in constructing the buildings for a long time along with human history.
In particular, comparing to stone or wood, soil has been used as a building material since ancient times because it is a common material which can be obtained everywhere. However, because it is poor in the mechanical strength and durability as a building material and because it has a poor image in its appearance, it has not been used as a mainstream material as compared to stone or wood.
However, since various bio-friendly and eco-friendly characteristics of soil have been newly recognized, soil is receiving the attention as a building material in the future.
In other words, the processing materials such as concrete, which are widely used as building materials today, destroy the nature from the manufacturing process and consume a large amount of energy, which result in increase of the emissions of carbon dioxide, which is a pollutant, as well as concrete wastes generated during the dismantling process contaminate the soil and damage the natural ecosystems in the end. In comparison, even if the soil buildings are dismantled after the life of the building has ended, the soil returns to the nature as it is, which can emphasize that there is no risk of corrupting or contaminating the natural ecosystems. In this point, the soil can be said as a representative of environmentally friendly materials more than anything.
In addition, as all living organisms are born from the soil and return to the soil, all organisms are inseparable from the soil. Therefore, the building which is mainly composed of the soil function as a space of a comfortable life, which is based on the various characteristics of the soil good for the human body, such as the functions of automatic temperature and humidity control, sterilization and deodorization, and radiation of far-infrared, which we can say that the soil is a bio-friendly material.
As stated above, while the soil has various eco-friendly and bio-friendly advantages, due to plain and simple appearance as well as other issues in robustness and durability, the soil has been used as the building materials with improved strength and durability such as bricks by burning the soil or by processing the soil with settlement agents.
However, in these building materials, the natural characteristics of soil are weakened or changed, let's leave them out of the discussion. If we examine the conventional construction methods using the soil as a main material, it is roughly classified into the wet construction methods and the dry construction methods.
First, the dry construction method can be divided into masonry type and compaction type. The masonry type is a method of construction to lay up block bodies, that are made by molding the soil inserted into the frame, using the methods such as bricklaying while the compaction type is a method of construction where the soil is filled into a form and compacted using a pounder and others, and this process is repeated to fill and compact the soil for constructing the wall.
As explained above, as the dry construction method does not use the water during the construction process, any separated drying process is not needed, as well as it does not demand any special construction technology. For this reason, it has an advantage of easy-to-construct, but this type of structure is weak against the lateral forces such as shear force, which has inefficient aspects of unnecessarily requiring a thicker wall and extremely low seismic performance and this structural weaknesses prevents this construction method from application to the large size buildings higher than the second floor.
Next, the wet construction methods include the pugging clay paint-over method, soil spray method, and recently developed pugging clay filling method.
Of these methods, the pugging clay paint-over method that has been used since ancient times, is a method to construct the wall by repeating the manual process daubing with the pugging clay inside and outside the core material which was made by weaving the plants such as stalks of millet.
It can be said that this method has been progressed one step in view of having reinforced the shear force and the earthquake resistance which are the greatest weaknesses of the construction of soil by enhancing the core material, however, due to a matter of primitiveness and effort of manual labor, the soil spray method where lath steel meshes instead of the core material of plants are arranged on the form materials and the soil and water or pugging clay are sprayed for paint-over using the mechanical equipment such as in shotcrete is partially used these days.
However, the so called dry construction method using this method where spraying the soil and water separately, has a problem that the soil is washed away during the process of spray or the soil is not properly kneaded, while the so called wet construction method where spraying pugging clay, has a problem that the mechanical equipment has often troubles by stuck clay due to its viscosity, which limits its application only to covering the soil wall thinly on already constructed wall and cannot be utilized for regular wall construction.
Finally, the pugging clay filling method is a construction method which has been recently developed and registered by this inventor as the Korean Patent No. 10-1003371 (Dec. 16, 2010) as a prior art considering the problems in the conventional wet construction as described above.
The prior invention described above regards to the frame member (10) composed of cage shaped wire mesh which is connected by a number of grid nets (13) between the front nets (11) and the rear nets (12) which are installed oppositely each other as shown in FIG. 1. This frame member performs the functions of the form and the reinforced rebar at the same time, if compared to concrete work.
The above described frame member is able to function as a shape retaining member without the formwork, which results from the clay specific-viscosity and plasticity which are realized when the soil becomes pugging.
In other words, unlike the concrete kneading which has a distinguished liquidity, if the pugging clay is poured into the frame member due to its strong viscosity and plasticity compared to liquidity, the pugging clay not only sticks on dense nets composed of wire mesh but also is not easily pushed out of wire mesh due to the plasticity that tends to maintain its form as long as the external force does not act.
Therefore, it can be considered that the prior invention has devised a new construction method for innovative structural form making the most of properties of the clay, however, the clay-specific viscosity and plasticity act as a double edged sword in the actual construction process as described above, and result in the reduced efficiency, which should be improved.
In other words, if we try to pour the pugging clay into the frame member, the pugging clay gets stuck immediately to wire mesh by the viscosity as described above, and if we try to mince the pugging clay using a pestle, the shape gets only distorted due to its unique plasticity, which makes it difficult to fill the frame member densely.
After all, this method has a problem that the construction efficiency gets significantly reduced in terms of construction period and manpower, because the work must be carried out manually one by one with hand tools in order to pour properly the pugging clay into the frame member. The existing mechanical spray method also exposed the same problem in the conventional spray method.